This invention relates to an air-conditioning system in which heating medium water is heated by solar heat obtained by a solar heat collecting unit and thus heated warm water is circulated,
(i) in the cold season for which heating is required, directly to an air-conditioning unit for heating purposes, or
(ii) in the hot season for which air-cooling is required, to an absorption type refrigerating machine as a driving heat source, thereby to obtain cold water, which is subsequently circulated to the air-conditioning unit for air-cooling purposes, and when solar heat cannot be obtained in rainy or cloudy days or when the air-conditioning load for a space to be air-conditioned becomes too much, an air-cooling and heating apparatus of high efficiency may back up the air-conditioning effect.
There has conventionally been known this kind of air-conditioning system, for example, as shown in FIG. 1, in which warm water heated by a solar heat collecting unit 1' and stored in a regenerator tank 2' through a circulating pump P1' is circulatingly supplied, as a heat source, through a pump P2' to a generator 4A' of a warm water heating absorption type refrigerating machine 4', which is connected to a cooling tower 6' through a pump P3'. In this refrigerating machine 4', a refrigerant contained therein such as ammonia or lithium bromide is repeatedly subjected to a refrigerating cycle of evaporation-condensation-vaporization-absorption, thereby to provoke a cooling action, thus producing cold water.
In the hot season for which air-cooling is required, thus produced cold water is circulatingly supplied to a fan coil unit 10' disposed in a space to be air-conditioned S', through a cold water circuit 17' by a pump P4' for air-cooling the space to be air-conditioned S'. On the other hand, in the cold season for which heating is required, the warm water in the regenerator tank 2' is not supplied to the refrigerating machine 4' but circulatingly supplied to the fan coil unit 10' through a warm water circuit 18' by the pump P2' for heating the space to be air-conditioned S'.
Naturally, three-directional switch valves are disposed at points a' and b', respectively, for switching the circulating path of warm water from the regenerator tank 2'. However, as a source of energy for air-cooling and heating, such a conventional system has fully relied on only solar heat obtained by the solar heat collecting unit 1', and a boiler 23' is used for providing air-conditioning in the case no solar heat is available. In such a conventional system, following inconveniences have therefore been noted:
(i) Air-conditioning load greatly varies throughout the year. In a conventional system, the solar heat collecting unit 1' has to be designed to have a solar heat collecting capacity covering the maximum air-conditioning load in the year, thus requiring a great number of solar heat collector plates, so that the solar heat collecting unit 1' itself becomes large-sized.
(ii) Not only the air-conditioning load but also solar radiation vary throughout the year, thus requiring the regenerator tank 2' having a considerable capacity in order to always provide appropriate air-conditioning.
(iii) It requires a boiler 23' having a capacity approximately as much as that of a usual air-conditioning system utilizing no solar heat to provide appropriate air-conditioning when no solar heat can be collected at all in a cloudy weather or during the night.
By reason of the above (i) to (iii), the cost of equipment for the solar heat collecting unit 1', regenerator tank 2' and boiler 23' has become very expensive.
Furthermore, in the intermediate seasons, and at the begining and end of the air-cooling or heating season, collected solar heat energy has been larger than the required air-conditioning load and the surplus solar heat has been wasted without being utilized.
Although solar heat has been utilized for the purpose of energy-saving, variations in the air-conditioning load and solar radiation throughout the year have thus resulted in increased cost of equipment and rendered collected solar heat futile. A very long period of time has therefore been required for repaying the cost of equipment, so that such a conventional system has not actually been economical from the viewpoint of the life-time of the system.
Since such a conventional system has been formed large-sized, a broad installation place has been required and piping cost has subsequently been increased.
In addition, because of the necessity to dispose various units each having a high capacity, much power energy has been required also for circulating pumps.
Furthermore, in order to dehumidify, cold water of 6.degree. to 8.degree. C. is required. In this connection, in order to provide cold water of a temperature as low as 6.degree. to 8.degree. C. at the outlet of the warm water heating absorption type refrigerating machine 4', the temperature of the heating medium (warm water supplied from the regenerator tank 2') should be 80.degree. C. or more. This becomes apparent from FIG. 2 (a) and (b) showing the relationship of the cold water outlet temperature T(.degree.C.) with respect to the chiller COP (coefficient of performance) and the refrigerating capacity P (Kcal/h) with the warm water inlet temperature (.theta.) as parameter (.theta.1=100.degree. C., .theta.2=95.degree. C., .theta.3=90.degree. C., .theta.4=85.degree. C., .theta.5=80.degree. C., .theta.6=75.degree. C.). Consequently, the temperature of the regenerator tank warm water for operating the refrigerating machine 4' has had to be kept high, and the temperature difference between the heat collecting unit 1' and the regenerator tank 2' has subsequently been small, thus resulting in a low heat collecting efficiency, which has made the depreciation period of the system further longer.
When no solar heat is available, the refrigerating machine 4' has to be operated by heated water supplied from the boiler 23'. Therefore, the whole efficiency has become 45 to 50% (the boiler efficiency of about 75% multiplied by the refrigerating machine's COP of 0.6 to 0.7), resulting in great waste of energy.